The field of optical switching has been established for many years. Incorporated in this field have been inventions used in connection with the printing and automatic control fields as well as the camera or photographic art. What is required in most cases is a controllable or selectable interruption of a light path or part of a light path.
These prior art devices teach the use of electrical circuits incorporating electromagnetic control devices for motivating and/or controlling the position of an opaque, metallic member to interrupt the light path. In many instances, the opaque, metallic member is mechanically biased to a fixed or stable position. The electromagnetic attractive forces induced into the machine overcome this mechanical bias to position the member into or out of the optical path. These devices thusly become quite complicated and intricate to build and are at best monostable in their operation, requiring constant power to maintain the elective control position.
Other devices such as those designed for automatic exposure controls in photographic cameras include photocell controlled multivibrators. These devices are neither capable of completely closing off one light path while opening another light path nor capable of bistable operation. Moreover, these instruments are usually quite delicate. In each instance, the magnetic forces act against a mechanical spring or other biasing member.
One consideration for error that the prior art devices above possess is that they invariably use separate light paths for reference and sample measurement readings. As transmission qualities of each path must deteriorate unequally, an error may be introduced into an instrument due to degradation of the optical paths.
An object of this invention, therefore, is to provide a bistable optical switch.
Another object of this invention is to provide such a switch having distinct and discrete complimentary states similarly to an electrical flip flop.
Another object of this invention is to provide a switch using a common light path for reference and sample instrument readings.
Another object of this invention is to provide such a switch for fiber optic application, wherein the switch may be economically constructed.
A further object of this invention is to provide a switch having as few as a single moving part.
A further object of this invention is to provide a multiposition discrete output optical switch having multiple stable states requiring neither mechanical biasing nor electrical power for maintaining switch states.